The measurements of spatially localized rapid temperature changes are required in studies of many physical and biological processes and objects. These can include such diverse subjects as turbulent flows, changes associated with processes of explosion and combustion, microtemperature measurements in biology at the cellular and subcellular level and microtemperature measurements in evolving chemical reactions. For all these applications a microthermocouple is the most convenient detector.
In recent publications, fast microthermocouples have been described with response times of milliseconds and spatial resolutions of from hundreds [L. J. Forney, E. L. Meeks, J. Ma, and G. C. Fralick, Rev.Sci.Instrum. 64, 1280 (1993)] to tens [P. Beckman, R. P. Roy, K. Whitfield, and A. Hasan, Rev.Sci.Instrum. 64, 2947 (1993)] of micrometers. Such microthermocouples may also be used as point radiation microdetectors in a range of wavelengths from the UW to the IR.
In addition to the above Pendley and Abruna [B. D. Pendley and H. Dl Abruna, Anal. Chem. 62, 782 (1990)] have considered the problem of microelectrodes for microchemical measurements and achieved outer diameters of a few microns under non-reproducible conditions. In addition, micromagnetic measurements are made using magnetic wires that are electropolished in which it is difficult to construct such tips [K. Sueoka, F. Sai, K. Parker and J. Arnolddussen, J. Vac.Sci. and Tech. B12, 1618 (1994)]. Furthermore, there is great interest in making microtip field emission tips [C. A. Spindt, et al. J. Appl.Phys. 47, 5248 (1976)] but there is an active interest in new methodologies for making such tips with better characteristics.